1. Field of Invention
The present invention pertains to carburetors for use in internal combustion engines, specifically carburetors including a metering block attached to the side or sides of the carburetor and a float bowl attached to the side of the metering block.
2. Prior Art
In the past, carburetors have been provided for delivering a predetermined, calibrated mixture of air and fuel into the intake manifold of an internal combustion engine. Fuel that is to be mixed with air and delivered through the carburetor to the engine is typically introduced into a reservoir known as a fuel bowl and metered directly into the intake manifold of the engine through one or more orifices, known as fuel jets or just jets, mounted in the carburetor. The diameter of the orifice in the fuel jets controls the amount of fuel that may be metered into the engine under a given set of operating characteristics. Because of this, fuel jets are frequently changed to jets having different size orifices to recalibrate the air to fuel ratio of the engine to achieve specific performance goals. Thus, the orifice diameter of the fuel jets is an important factor to be taken into account when “designing or setting up” a carburetor for a given application.
The factory location of the jets is inherently bad, due to its location being parallel to vehicles braking and acceleration axis, and is subject to becoming uncovered by fuel, causing the engine to starve for fuel during hard acceleration, deceleration, and cornering.
In order to change the jets in existing carburetors such as those manufactured by Holley.RTM. And Demon.RTM., it has been necessary to physically remove the fuel reservoir or float bowl to gain access to the jets so that they can be removed and changed to the desired jet configuration. However, before the fuel reservoir can be removed, it is necessary to somehow drain the float bowl or allow the fuel contained in the fuel bowl to simply escape when the bowl is removed from the carburetor. Because carburetors are typically mounted on top of the engine, fuel escaping from the carburetor onto the engine creates a fire hazard, especially when the engine is hot. Because of this, removal of the float bowl from a carburetor in a hot engine creates a significantly hazardous situation, both for the mechanic and those in the surrounding area. Another difficulty associated with the removal of the float bowl is that such removal often damages a gasket provided between the fuel bowl and the mating structure of the carburetor and must be replaced prior to reassembly of the float bowl to the carburetor.
In certain automotive applications, such as racing for example, it is important to be able to rapidly change the jets within the carburetor to fine tune the engine performance for the particular application. With regard to racing applications, variations in track conditions and atmospheric conditions, such as humidity and barometric pressure for example, make it desirable to have the ability to rapidly gain access to the carburetor jets to change them to jets that are appropriate for the particular track and atmospheric conditions. For example, during qualifying for a race, mechanics will typically fine tune the engine to achieve the optimal performance and thus achieve the fastest qualifying time by changing the fuel jets until the optimum engine performance is obtained. The dynamic nature of such a qualifying session demands that jet changes be performed rapidly in order to get the car back on the track as soon as possible. Moreover, during actual racing situations, it is frequently desirable to have the ability to affect rapid jet changes to compensate for changing track and atmospheric conditions or for other performance related reasons, such as fuel economy, for example.
Attempting to change the fuel jets under the demanding circumstances of prerace qualifying and actual racing situations has not been entirely successful because of the safety hazards associated with the removal of the fuel bowl from the carburetor to access the metering jets, as well as the time involved in physical removal and replacement of the fuel bowl. Even assuming that the gasket does not have to be replaced after removal of the fuel bowl, it still takes a significant amount of time to physically unbolt the fuel bowl and change the metering jets. This amount of time can be critical in qualifying and actual race situations. Holley.RTM. has produced an alternative style of float bowl for its carburetors that contains two screw-in plugs which are aligned with a vertical center line of each of the two jets associated with the primary and secondary venturies in its four-barrel carburetor design. The removable screw-in plugs allow access to the jets as they are retained in their normal position in the metering block without removing the float bowl. However, the screw-in plug arrangement for accessing the jets still requires the fuel to be drained from the float bowl before the plug is removed; otherwise, the potential hazard of flammability remains.
Inventor Crum U.S. Pat. No. 4,100,663 1978, addressed this with a kit installing 90 degree angle fittings into the metering block to allow the jet to face upwardly, drilling holes in the existing float bowl above the jets and adding plugs to the top of the float bowl. The jets are screwed into the top of the 90 degree fitting. This caused the jets inlet to be raised and causes fuel starvation to be increased. The float level would then need to be adjusted higher to compensate for the starvation. This causes raw fuel to slosh into the main body venturi during normal deceleration and acceleration, causing extreme rich conditions, engine cutout and possible fire due to backfire.
Inventors Hammel U.S. Pat. No. 5,776,377 1998, and Noguez U.S. Pat. No. 4,277,423 1981 addressed this by replacing the original metering block with one that contains the metering jets in a removable jet cartridge within a metering block that would replace the original equipment metering block provided on carburetors such as those designed by Holley.RTM. Replacing the manufacturer's metering block with an aftermarket unit may have adverse affects on the factory calibration of the metering block function.
Accordingly, it would be desirable to provide a system whereby the fuel jets could be readily removed from the carburetor assembly without the need to drain the carburetor or remove the fuel bowl to effect the change. It would be particularly desirable if the metering jets could be removed from the top of the carburetor bowl that would replace the original equipment fuel float and fuel bowl provided on carburetors such as those designed by Holley.RTM. and Demon.RTM Corporations, to permit rapid jet removal and replacement in those applications, yet still using the manufacturer's calibrated metering block, particularly racing, that require rapid change-outs.
The function of the metering block in a typical Holley.RTM, or Demon.RTM, carburetor is to control the amount of fuel which is delivered to an internal combustion engine by limiting fuel volume through a series of replaceable and non-replaceable orifices. The replaceable orifices are commonly known as jets. Jets typically have a portion of machine screw threads on one end and a slotted configuration on the other end to facilitate removal and installation with a standard flat blade screwdriver. The jets are identified by the diameter of the orifice contained therein. Those operating Holley.RTM. or Demon.RTM carburetor, commonly change these jets to change the amount of fuel consumed by an internal combustion engine.
Fuel that is metered by the jets is introduced into a vertical chamber that is cast into the metering block. This chamber is commonly known as the main well. Fuel entering the main well enters at the bottom where the jets are located. As previously mentioned, the jets are retained in the metering block by their machine screw threads, and are exposed to a fuel supply contained within a float bowl or a fuel bowl. Under operating conditions, the fuel bowl contains a small reservoir of fuel which is maintained and made available to the jets under normal atmospheric pressure and gravity. There is also a float control valve typically contained within the fuel bowl which allows the fuel entering the fuel bowl to be maintained at a relatively constant level within the bowl.
After fuel has passed through the jets and into the main well, a metered amount of air is introduced into the main well to mix with the fuel. This process of introducing air into the fuel is commonly referred to as “emulsion.” As this process takes place, the fuel in the main well that is emulsified travels vertically upward until it reaches the height of a main well discharge passage, which is typically located near the top of the metering block. At this point, the emulsified fuel mixture exits the metering block and enters a passage commonly referred to as the main discharge nozzle where it enters and mixes with the air being consumed by the engine.
The entire mechanism for metering, emulsifying, and delivering of fuel to the carburetor's main discharge nozzle exists in a pair of identical mirror image configurations for two and four venturi carburetor applications. The venturies associated with a carburetor are commonly referred to as barrels such that a four venturi carburetor is referred to as a four-barrel carburetor. The metering blocks are configured to work in conjunction with two venturies at once. Thus, a two-barrel carburetor requires one fuel float and fuel bowl, whereas a four-barrel carburetor requires two fuel floats and two fuel bowls.